Survey Shows STRmix™ Has Been Used in 220,000 Cases Worldwide

A recent survey indicates that STRmix™ – sophisticated forensic software for resolving mixed DNA profiles previously thought to be too complex to interpret – has now been used in at least 220,000 cases worldwide since its introduction in 2012.

Conducted by New Zealand’s Institute of Environmental Science and Research (ESR), the survey also shows that STRmix™ evidence was presented in more than 80 successful admissibility hearings worldwide – double the survey number reported the year before.  

“Demand for STRmix™ has been extremely high due to the critical role it plays in helping to solve crimes and excluding individuals who have been wrongly associated as the source of crime scene evidence,” says John Buckleton DSc, FRSNZ, Forensic Scientist at the New Zealand Institute of Environmental Science and Research (ESR) and one of the developers of STRmix™.

Dr. Buckleton notes that STRmix™ has proven to be highly effective in producing usable, interpretable, and admissible DNA results in a wide range of criminal cases, including violent crime and sexual assault cases. It has also been instrumental in helping to solve cold cases in which evidence originally dismissed as inconclusive was reanalyzed, helping to develop investigative leads and support exonerations in post-conviction cases.  

On the development side, the ESR survey indicates that there is significant interest among forensic laboratories currently using STRmix™ in a solution for probabilistic genotyping of Y-STR (male-specific DNA) profiles. There is also a desire for more advanced probabilistic genotyping and foundational likelihood ratio (LR) training, demonstrating that STRmix™ users want a more in-depth understanding of STRmix™ principles.

“STRmix™ has responded to that demand by scheduling six training workshops for the fourth quarter of 2020 and already booking an additional four workshops for 2021,” says Catherine McGovern, Training and Support Leader at STRmix™.  

McGovern notes that due to COVID-19 travel restrictions, all STRmix™ training is now being conducted remotely. “Despite the pandemic, the majority of STRmix™ users have indicated strong interest in online, WebEx-style training courses,” she explains.

STRmix™ is currently in use in 59 organizations in the U.S., including the FBI, the Federal Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF), and numerous state, local, and private forensic laboratories. It is also in various stages of installation, validation, and training in more than 60 other organizations.

A new version of STRmix™, STRmix™ Version 2.8, was recently launched following nearly a year of extensive development and testing. STRmix™ v2.8 features a top-down approach that allows users to set the number of major contributors to a mixed DNA profile in which there is interest, and then obtain the LR only for those contributors. This approach enables users to tackle more complex profiles faster. The new version of STRmix™ also contains improved modelling and memory usage.

The team that created STRmix™ has also released two other products: DBLR™, an investigative application used with STRmix™ which allows users to undertake superfast database searches, visualize the value of their DNA mixture evidence, and carry out mixture to mixture matches; and FaSTR™ DNA, expert forensic software that rapidly analyzes DNA profiles and can assign a number of contributors (NoC) estimate.

Designed by scientists for scientists, FaSTR™ DNA combines an intuitive, user-friendly graphical interface with easily understandable and laboratory-customizable rules to expedite the analysis of raw data generated by genetic analyzers and standard profiling kits. It also optionally implements the use of artificial neural networks for peak classification independent of and in parallel to the forensic analyst.

Alongside STRmix™, FaSTR™ DNA and DBLR™ complete the full workflow(external link) from analysis to interpretation and database matching.